Indoor Air Quality (Iaq); Iaq (Analog Input); Iaq (Switch Input) - Carrier 48HC 04-28 Controls, Start-Up, Operation And Troubleshooting

calculated outside air CFM falls below Power Exhaust Stage1
CFM (PE1.C). The Power Exhaust Stage2 CFM (Configura-
 
tion ECON PE2.C) is not currently used on these products.

Indoor Air Quality (IAQ)

The ComfortLink control has the capability for several meth-
ods of demand ventilation control. Indoor air quality is typical-
ly measured using a CO sensor whose measurements are dis-
2
played in parts per million (ppm). Outdoor air quality may be
measured with a CO sensor for indoor-outdoor differential de-
2
mand ventilation control, or with other sensor types for the out-
door air lockout function. The factory-installed indoor air qual-
ity CO sensor is mounted in the return section. A field-in-
2
stalled indoor air quality CO
return duct or directly in the occupied space, per job require-
ments. The indoor air quality modes of operation can be affect-
ed by configurations for indoor air quality sensor (Configura-
 
tion AIR.Q IA.CF), indoor air quality switch (Configura-
 
tion AIR.Q II.CF), outdoor
 
(Configuration AIR.Q
limit configurations as described below.

IAQ (ANALOG INPUT)

The ComfortLink control is configured for indoor air quality
sensors which provide 4 to 20 mA signal for 0 to 2000 ppm
CO . If the sensor being used has a different range, the ppm
2
display range must be reconfigured by entering new values for
the IAQ Sensor Value
 
tion AIR.Q I.4M) and IAQ Sensor Value at 20mA (Config-
 
uration AIR.Q I.20M).
IA.CF = 0 (No IAQ)
IA.CF = 0 signifies that there is no IAQ sensor installed. The
damper will operate at the Econ Min at Max Fan Speed (Con-
 
figuration ECON MP.MX) when the fan is at Supply Fan
Maximum Speed (Configuration
damper position will vary at other fan speeds as described in
the Economizer section, when the space is occupied and the in-
door fan is on.
IA.CF = 1 (DCV)
When IA.CF = 1, the IAQ algorithm is set for Demand Con-
trolled Ventilation (DCV). During DCV, the damper modulates
between two user configurations depending upon the relation-
ship between the Indoor Air Quality (IAQ) and the Outdoor
Air Quality (OAQ).
The lower of these two positions is referred to as the Econo
Min IAQ Position (Configuration
the higher is referred to as the Econ Min at Max Fan Speed
 
(Configuration ECON
sition (AQ.MN) should be set to an economizer position that
brings in enough fresh air to remove contaminates and CO
generated by sources other than people. The Econ Min at Max
Fan Speed (MP.MX) should be set to an economizer position
that brings in fresh air to remove contaminates and CO
ated by all sources including people when the indoor fan is op-
erating at the Supply Fan Maximum Speed (Configura-
 
tion I.FAN FS.MX). The Econ Min at Max Fan Speed
(MP.MX) value is the design value for maximum occupancy.
The ComfortLink controls will begin to open the damper from
the Econo Min IAQ Position (AQ.MN) position when the IAQ
level begins to exceed the Outdoor Air Quality (OAQ) level by
a configurable amount. This amount is referred to as AQ Dif-
ferential Low (Configuration
differential between IAQ and OAQ reaches AQ Differential

High (Configuration AIR.Q
sition will be at the Econ Min at Max Fan Speed (MP.MX)
when the indoor fan speed is at Supply Fan Maximum Speed
(FS.MX). When the IAQ/OAQ differential is between AQ Dif-
ferential Low (AQD.L) and AQ Differential High (AQD.H),
the control will modulate the damper between Econ Min at
Max Fan Speed (MP.MX) and Econo Min IAQ Position
sensor may be mounted in the
2
air quality
OA.CF) and other related fan and
at 4mA (Configura-
 
I.FAN FS.MX) and the
 
AIR.Q AQ.MN), while
MP.MX). The Econo Min IAQ Po-
 
AIR.Q AQD.L). When the

AQD.H), the economizer po-
(AQ.MN) in a linear manner as shown in Fig. 8. At other fan
speeds the economizer damper will operate in the shaded area
between the two economizer position curves but at the actual
fan speed as indicated by Commanded Fan Speed (Out-
 
puts FANS
ECON MIN
AT MAX
FANSPEED
POSITION
(MP.MX)
MINIMUM
IAQ
DAMPER
sensor
POSITION
(AQ.MN)
Fig. 8 — Economizer Minimum Position
IA.CF = 2 (Override IAQ)
When IA.CF = 2, the IAQ algorithm maintains the damper at
Econ Min

tion ECON
ply Fan Maximum Speed (Configuration
or along the curve on Fig. 8 when the indoor fan speed is at the
Commanded Fan Speed (Outputs
override condition triggers. The override triggers when the
IAQ/OAQ differential is greater than AQ Differential High
(Configuration
tion (Configuration
tion during override. The economizer damper will return to the
Econ Min at Max Fan Speed (MP.MX) or MP.MX curve at oth-
er fan speeds when the IAQ/OAQ differential is less than the
AQ Differential Low (Configuration
The override algorithm will operate whenever the building is
occupied and the indoor fan is operating or whenever the IAQ
algorithm has caused the indoor fan to operate. The IAQ Ana-
log Fan Config (Configuration
whether or not the IAQ algorithm can turn on the indoor fan. If
the indoor fan is not operating, the economizer position will be
zero. If the override is not active and the building is unoccu-
2
pied, the economizer position will be zero. The damper posi-
tion may exceed Econ Min at Max Fan Speed (MP.MX) or IAQ
gener-
Override Position (OVR.P) to provide economizer cooling.
2
IA.CF = 3 (Control Minimum Position)
When IA.CF = 3, an external 4 to 20 mA source is used to set
the minimum position. The 4mA signal corresponds to 0% and
the 20 mA signal corresponds to 100%. In this mode, configu-
rations such as Econ Min at Max Fan Speed (Configura-

tion ECON

ration AIR.Q
tion and DCV minimum position curves in Fig. 7 and 8 are not
used. If the indoor fan is not operating, the economizer position
will be zero. The damper position may exceed the economizer
minimum position to provide economizer cooling.

IAQ (SWITCH INPUT)

Indoor air quality can also be measured using a switch input. For
the purpose of specifying the type of switch input, low CO
els are considered normal. The IAQ switch input is defined by
27
F.SPD). (See Fig. 8.)
VENTILATION FOR PEOPLE
VENTILATION FOR SOURCES
1 0 0 7 0
AQ AQ
DIFFERENTIAL DIFFERENTIAL
LOW (AQD.L) HIGH (AQD.H)
at Max Fan Speed

MP.MX) when the indoor fan speed is at Sup-

FANS
 
AIR.Q AQD.H). The IAQ Override Posi-
 
AIR.Q OVR.P) sets the damper posi-

AIR.Q

AIR.Q

MP.MX), Econo Min IAQ Position (Configu-

AQ.MN) and the economizer minimum posi-
0 N I S D I / E O U T S D I E C O
2
DIFFERENTIAL
(Configura-
 
I.FAN FS.MX)

F.SPD) until the

AQD.L).

IA.FN) determines
lev-
2